This proposal is a pilot study to begin to evaluate the hypothesis that there is a subgroup of inner city patients with asthma who are particularly sensitive to the health effects of ambient air pollutants and to identify these patients by the elaboration of specific biomarkers. We will take advantage of a unique opportunity to prospectively follow subjects with asthma and daily ambient pollutant counts derived from a planned New York State Department of Health and NYS Department of Environmental Conservation study. We will assess whether there are biologic markers that can be used to identify subjects who are particularly sensitive to the effects of environmental air pollutants (ozone; O3, and particulate matter; PM10). Since hospital use is an insensitive indicator of asthma morbidity, we will prospectively follow a cohort of patients with moderate-severe asthma who reside in the area of the 14th Street pollutant monitoring area and evaluate the effects of ambient elevations of O3 and PM10 on symptom and functional status (daily diary, peak flow). To determine whether biomarkers associated with an immune asthma response are altered during periods of high or low O3 and PM10, we will monitor baseline (low O3, PM10) levels of serum and nasal lavage levels of interleukin 4 (IL-4) and interferon-g (IFN-g ) and nasal lavage and epithelial cell production of granulocyte-macrophage colony-stimulating factor (GM-CSF). These subjects will then be followed prospectively during high and low O3 and PM10 days, and alterations in cytokine levels will be determined.